|Publication number||US7599797 B2|
|Application number||US 11/350,655|
|Publication date||Oct 6, 2009|
|Filing date||Feb 9, 2006|
|Priority date||Feb 9, 2006|
|Also published as||US20070203648|
|Publication number||11350655, 350655, US 7599797 B2, US 7599797B2, US-B2-7599797, US7599797 B2, US7599797B2|
|Inventors||Benny Poedjono, Tamara San Antonio|
|Original Assignee||Schlumberger Technology Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (21), Referenced by (7), Classifications (15), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The invention relates generally to methods for planning and drilling wells.
2. Background Art
For every well drilled in a given field, the objective is to intersect a potential successful. As the number of wells in the field increases, the possibility of the well being drilled (subject well) colliding with neighboring wells (offset wells) in the field increases. Catastrophic events, which may lead to injury to and/or loss of human life, can accompany well collision. Therefore, it is imperative that the risk of well collision is minimized.
Traditionally, methods for minimizing risk of well collision involve optimizing design of the subject well such that a minimum separation distance exists between the subject well and offset wells. However, even if the subject well is designed such that a minimum separation distance exists between the subject well and the offset wells, there may still be a risk of well collision due to uncertainties in the survey data for the offset wells. Thus, a detailed and continuously updated drilling plan is needed to minimize the risk of well collision through the course of drilling the subject well.
During planning and drilling of a subject well, an anti-collision scan is run on the well design to determine if there is a risk of well collision. Risk of well collision may be expressed in terms of minimum separation distance between the subject well and offset wells. If there is a risk of well collision, a request is made for an anti-collision standard exemption. If the request is granted, then the well can be drilled according to the conditions stated in the grant. Depending on the congestion level in the field, numerous anti-collision standard exemption requests may be filed during planning and drilling of a single well.
Each processing of an anti-collision standard exemption request requires gathering of data from offset wells, followed by analysis of the data by a professional to design a safe and drillable well. The data gathering and analysis are laborious, often requiring extensive manual input, hence subject to human error. The data and analysis related to processing of anti-collision standard exemption requests for one well is typically not applied to processing of anti-collision standard exemption requests for the next well in the same field. As a result, mitigation of risk of collision of the next well is just as laborious as for the previous well.
From the foregoing, a more efficient process of mitigating risk of well collision in a field is desired.
In one aspect, the invention relates to a method of mitigating risk of well collision in a field which comprises receiving an anti-collision standard exemption request containing a description of risk of collision between a subject well and one or more offset wells, generating an assessment of the anti-collision standard exemption request using a multidimensional decision matrix, reviewing the assessment, and selectively updating the decision matrix based on the review.
In another aspect, the invention relates to a system for mitigating risk of well collision which comprises a multidimensional decision matrix comprising actions to prevent likelihood of risk of collision and/or actions to mitigate risk of collision and a tool which receives an anti-collision standard exemption request and generates an assessment of the anti-collision standard exemption request using the multidimensional matrix, wherein the anti-collision standard exemption request comprises a description of risk of collision between a subject well and one or more offset wells.
In another aspect, the invention relates to a system for mitigating risk of well collision which comprises a media containing a program which when executed receives an anti-collision standard exemption request and accesses a multidimensional decision matrix to generate an assessment of the anti-collision standard exemption request, wherein the anti-collision standard exemption request comprises a description of risk of collision between a subject well and one or more offset wells, wherein the multidimensional decision matrix comprises actions to prevent likelihood of risk of collision and/or actions to mitigate risk of collision.
Other features and advantages of the invention will be apparent from the following description and the appended claims.
The invention will now be described in detail with reference to a few preferred embodiments, as illustrated in accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the invention may be practiced without some or all of these specific details. In other instances, well-known features and/or process steps have not been described in detail in order to not unnecessarily obscure the invention. The features and advantages of the invention may be better understood with reference to the drawings and discussions that follow.
A method of mitigating risk of well collision includes running one or more anti-collision scans during the course of planning and/or drilling a subject well. The anti- collision scan helps to determine if and where along the subject well an anti-collision standard is violated. The term “anti-collision standard,” as used herein, refers to a set of rules that apply globally and contain a detailed explanation of the survey-related requirements to be fulfilled in the well design and drilling process. The anti-collision standard may vary from one drilling project to the next, but in general, the standard is intended to avoid collision between the subject well and offset wells. For example, an anti-collision standard may be based on separation factor (SF) and/or center-to-center distance between the subject well and offset well. SF is a measure of the separation distance between the subject well and offset well based on intersection of ellipses normal to the trajectories of the subject well and offset well. In
Running of the one or more anti-collision scans includes generating one or more anti-collision reports. An anti-collision report includes depths along the subject well where the anti-collision standard is violated. For example, if the anti-collision standard is SF <1.5, then depths where SF between the subject well and offset well(s) is less than 1.5 are reported. At each depth where there is a risk of collision with one or more offset wells, e.g., where SF <1.5, an anti-collision standard exemption request is made. If the request is granted, then the well can be drilled, but with modifications to the drilling plan. If the request is not granted, the well should not be drilled. Since there are uncertainties in data of offset wells, the method includes checking the integrity of survey data where an anti-collision standard is violated before recommending modifications to the drilling plan.
The process further includes quality check of the data stored in the central database for completeness, consistency, and accuracy (204). Questions that may be asked during the quality check include, but are not limited to, is the client, field name, and project identifier consistent throughout the data and does the survey data match the survey tool type? If the data is not complete, consistent, or accurate, the data is refined (206). This may include gathering more data or correcting data already gathered. Then, the quality check of the data is checked again (204). Updates made to the data are stored so that it is not necessary to repeat the same data refinement for future generation of anti-collision standard exemption requests (203).
If the data stored and/or updated in step 203 is complete, consistent, and accurate, an anti-collision standard exemption request is generated using the data (208). The process includes quality check and assurance of the anti-collision standard exemption request, i.e., whether the anti-collision standard exemption request is complete and accurate (210). If there is any missing or questionable information in the request, the process returns to step 206, where the input data is corrected and/or additional data is gathered. If the anti-collision standard exemption request is complete and accurate, the request is approved for processing (212).
The decision matrix is a multi-dimensional matrix. It includes at least two dimensions. In a preferred embodiment, it includes at least three dimensions. Each dimension of the decision matrix can be characterized by one or more parameters. The parameters of each dimension of the decision matrix can be as varied as desired and may be single-valued or multi-valued
The following examples are presented to further illustrate how the decision matrix works. The examples are not intended to limit the invention as otherwise described herein.
Suppose that the subject well is a directional well that has proximity with an offset well with a SF <1.5 and center-to-center distance of 30 ft (9.75 m) at measured depth of 3000 ft (914.4 m) and true vertical depth of 2500 ft (762 m). The mud weight to be used in the collision area is that to contain the formation been drilled under normal conditions. The offset well pressure is low due to well lifting mechanism (electric submergible pump—medium low pressure reservoir). Magnetic scan reports interference which must be accounted for the survey program. As a result the mud weight pressure will be higher than the well pressure. Thus, the risk of a collision reduces to financial concerns only. This assessment will trigger preventing actions at the well site to manage the likelihood of the event controlling the residual risk.
Suppose that the subject well is a directional well that has proximity with an offset well with a SF <1.5 and center-to-center distance of 32 ft (9.75 m) at a measured depth of 5000 ft (1524 m) and a true vertical depth of 3000 ft (914.4 m). The mud weight to be used in the collision area is that to contain the formation been drilled under normal conditions. The offset well pressure is high due to well lifting mechanism (gas lift—medium low pressure reservoir). Magnetic scan reports interference, which must be accounted for in the survey program. As a result, the mud weight pressure will be lower than the well pressure. In the event of a collision the risk is high to personnel and equipment. This assessment will trigger mitigations measures to reduce (or eliminate) the potential risk and also preventing actions at well site to manage the likelihood of the event controlling the residual risk.
In one embodiment, the multi-dimensional decision matrix also contains process paths that provide guidance to reassess the input data, e.g., survey-related data, that may be of concern. For example, if the well being drilled outside the guidelines is based on SF <1.5 and/or center-to-center distances, the anti-collision report will indicate such. If this occurs, the quality of the data used in generating SF and/or center-to-center distances for the subject well and offset wells are verified before continuing assessment of the anti-collision exemption request. As a result of the steps in gathering and performing quality control and assurance on the input data, the input data used in generating the anti-collision standard exemption request becomes increasingly refined and reliable.
The assessment of the anti-collision standard exemption request may include a brief description of what rule from the standard is being broken or why the exemption request is needed. The assessment may include a summary of the offset wells at risk of colliding with the subject well and the status of the offset wells, e.g., whether the offset well is active, inactive, natural flow, abandoned, and so forth. The assessment may also include a summary of the risks if well collision occurs, including an indication whether the well collision would be major or minor. The assessment includes conditions under which the exemption can be approved. These conditions are the set of actions determined from the decision matrix. The assessment may have one or more objectives. One example of an objective is to minimize risk to human life and the environment of well collision occurs.
The process of the invention is designed to optimize any and all data through a learning process. This process determines the quality of the input data based on the proposed path of the subject well and specifies adjustments to the further drilling plan as needed. These adjustments are guided by the creation of an anti-collision multidimensional decision matrix. The multidimensional decision matrix includes process paths that provided guidance for reassessing the input data that may be questionable. As a result of the steps in gathering and performing quality check and assurance on the input data, the input data becomes increasingly refined and reliable. The need to repeat the process of refining input data each time a new well is to be drilled is therefore minimized.
It will also be apparent to those skilled in the art that this invention may be implemented by programming on or more suitable general-purpose microprocessors, such as shown in
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
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|U.S. Classification||701/301, 175/61, 701/302, 175/45, 324/346, 166/245, 702/9, 33/304, 175/62, 702/7|
|Cooperative Classification||E21B47/00, E21B47/022|
|European Classification||E21B47/00, E21B47/022|
|Mar 27, 2006||AS||Assignment|
Owner name: SCHLUMBERGER DRIVE, TEXAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:POEDJONO, BENNY;SAN ANTONIO, TAMARA;REEL/FRAME:017714/0510
Effective date: 20060209
|Mar 6, 2013||FPAY||Fee payment|
Year of fee payment: 4